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Biomedical subjects

J Melbin

Publications and source records attributed to J Melbin.

8 recordsLinked to original sources
PubMed1989

The Korotkoff sound.

As the auscultatory method of blood pressure measurement relies fundamentally on the generation of the Korotkoff sound, identification of the responsible mechanisms has been of interest ever since the introduction of the method, around the turn of the century. In this article, a theory is proposed that identifies the cause of sound generation with the nonlinear properties of the pressure-flow relationship in, and of the volume compliance of the collapsible segment of brachial artery under the cuff. The rising portion of a normal incoming brachial pressure pulse is distorted due to these characteristics, and energy contained in the normal pulse is shifted to the audible range. The pressure transient produced is transmitted to the skin surface and stethoscope through deflection of the arterial wall. A mathematical model is formulated to represent the structures involved and to compute the Korotkoff sound. The model is able to predict quantitatively a range of features of the Korotkoff sound reported in the literature. Several earlier theories are summarized and evaluated.

Auscultation↗
PubMed1988

Baroreceptor responses derived from a fundamental concept.

A model is presented that relates the change in baroreceptor firing rate to a step change in blood pressure. This relationship is nonlinear since the alteration in rate of firing depends on the current rate of firing. It is shown that this simple relationship embodies all currently established baroreceptor response modes. The model needs refinement to allow for effects arising from the properties of the tissue matrix in which the receptors are embedded. Further analysis is precluded at present owing to paucity of quantitative experimental data.

Animals↗
PubMed1976

On a non linear describing function for bio-data.

The behaviour and handling of a flexible three variable--parameter function is presented, which is suitable for unbiased regression analysis. The function is defined by an intercept, a slope or coefficient and an exponent on the independent variable. Analog and digital problems and solutions are defined. Handling is simple and the program is run without operator intervention. The range of curves include linear, convex, concave and asymptotic forms and can be extended to include sigmoid and parabolic forms. Some application results are presented for different situations.

Computers↗
PubMed1975

Three dimensional laminar flow in distorting, axisymmetric, axially varying vessels.

Three dimensional laminar, viscid flow is developed for Newtonian fluids which provides absolute values for axial, radial and tangential velocity fields everywhere if the dimensions of the vessel are known and two simultaneous axial velocities e.g. on and off the central axis in the same plane, and the central axis velocity gradient are measured. In addition, normal and shear stresses are determinable. The equation set satisfies gemoetric and other known flow limiting conditions such as no slip at surfaces etc. and are amenable for inclusion in general, dynamic flow expressions. Alternatively they may be used alone for certain problems involving gradients and secondary flows. A range of illustrations are shown for a distorting vessel with elliptic cross-section and small axial taper (analogous to the pulmonary trunk during ejection).

Mathematics↗
PubMed1975

A new method for fabrication of latex cuffs.

A new and simple method is presented that is suitable for the fabrication of inflatable cuffs for any gross vascular size. The method lends itself to mass production which is particularly useful for the fabrication of small cuffs. The procedure generally consists of spraying latex on a rotating cylinder in two separable layers. An activating tube is inserted between the layers and the edges sealed. Outward expansion is prevented by means of a suitable backing material.

Methods↗